The present invention relates to a device for preventing a liquid from dripping from a filling nozzle for use in machines for filling containers with a specified quantity of liquid such as fluid food.
Filling machines of this type are known which comprise a metering cylinder housing a piston, a filling nozzle connected at its upper end to the metering cylinder, a check valve disposed in an intermediate portion of the filling nozzle between the upper and lower ends thereof for permitting a liquid to flow down through the filling nozzle but preventing the reverse flow of the liquid, and a porous member attached to the lower end of the filling nozzle for preventing the liquid from flowing down through the filling nozzle under gravity.
It is required that the filling machine be usable for some kinds of liquids which are different in viscosity, whereas when a single kind of filling nozzle is used for handling these liquids, it is likely that the porous member fails to completely confine the liquid within the nozzle, permitting the liquid to drip from the nozzle.
Devices are therefore known which comprise a check valve disposed in the filling nozzle and movable upward or downward by a change in the internal pressure of the metering cylinder produced by the operation of the piston, such that the upward movement of the valve creates a negative pressure in the space between the valve and the porous member inside the nozzle to thereby preclude the liquid from dripping from the nozzle.
With such devices, the upward and downward movement of the check valve is restricted by a flange, stepped portion or the like which is formed in the inner surface of the filling nozzle by machining. Accordingly, difficulty is encountered in making the valve movable a specified distance owing to errors involved in machining, making it impossible to obtain the desired negative pressure. If the negative pressure is lower than is desirable, the liquid will drip from the filling nozzle, while an excessive negative pressure is likely to draw air into the nozzle through the porous member.